Message-ID: <40835F4E.5000308@yahoo.com.au>
Date: Mon, 19 Apr 2004 15:10:38 +1000
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: Pedro Larroy <piotr@larroy.com>
CC: linux-kernel@vger.kernel.org
Subject: Re: CFQ iosched praise: good perfomance and better latency
References: <20040419005651.GA7860@larroy.com>
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Pedro Larroy wrote:
> Hi
> 
> I've been trying CFQ ioscheduler in my software raid5 with nice results,
> I've observed that a latency pattern still exists, just as in the
> anticipatory ioscheduler, but those spikes are now much lower (from
> 6ms with AS to 2ms with CFQ as seen in the bottom of
> http://pedro.larroy.com/devel/iolat/analisys/),
> plus apps seems to get a fair amount of io so they don't get starved.
> 
> Seems a good choice for io loaded boxes. Thanks Jens Axboe.
> 

Although AS isn't at its best when behind raid devices (it should
probably be in front of them), you could be seeing some problem
with the raid code.

I'd be interested to see what the graph looks like with elevator=noop
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